1. Field of the invention
The present invention relates to mobile robotic vehicles, particularly to robotic vehicles capable of operating in areas which are hazardous to humans.
2. Description of Related Art
The term robotic vehicle refers to a vehicle which has what may be called "robotic" features. In this context, "robotic" generally implies a mechanism which employs some level of computer control and sensory feedback. Another common term for robotic vehicle is mobile robot, and these will be used interchangeably in this application. One primary motivation for the use of robotic vehicles is to replace humans in areas which may be extremely hazardous. Examples include underwater, outer space, battlefield, and high-radiation nuclear environments. As the technologies related to design of robotic vehicles mature, their range of practical application will continue to grow.
A particular challenge in the art is to design a robotic vehicle which is able to maneuver in an obstacle-strewn environment. Depending upon the specific environment in which the vehicle is to be used, the vehicle should generally be able to climb stairs, traverse uneven surfaces, and cross obstacles in order to perform tasks, such as inspection and/or monitoring, throughout its working environment. The vehicle may serve as a platform for future man-machine interface, telepresence, and autonomous navigation experiments. Such vehicles will generally be operated remotely, for example, by tethering the vehicle to a power source and an external computer
Robotic vehicles are often categorized according to the type of locomotion they employ. Typically, mobile robots use wheels, tracks, legs, and in some instances, a combination of these. Wheeled systems are the simplest and most energy efficient of these types of locomotion systems. They can provide maximum maneuverability for hallways and restricted areas of buildings. They cannot, however, easily negotiate stairs or obstacles of significant height. Tracked or legged systems can be used to overcome the shortcomings of wheeled systems for surfaces which are soft or uneven. While tracked systems are preferable to legged systems from the viewpoint of simplicity of design and control, the crossing of some obstacles requires a legged locomotion system. For example, if a robotic vehicle were required to be able to climb obstacles of a given predetermined height and length or depth which may be on the order of 24 inches for an indoor environment, neither wheels nor tracks would suffice where the overall desired size of the vehicle must be relatively compact.
Hybrid systems aim to combine the advantages and minimize the disadvantages of two or more of the previously mentioned types of locomotion. One recent example of a hybrid robotic vehicle known in the art is the vehicle disclosed in U.S. Pat. No. 4,702,331, issued to Hagihara et al, and assigned on its face to Mitsubishi Denki Kabushiki Kaisha. That vehicle is provided with wheeled, tracked and legged modes of operation. While such a vehicle may therefore employ any of the three types of locomotion previously described, the vehicle does not have the capability of maintaining the body or platform of the vehicle in an upright and level position as it maneuvers across non-horizontal surfaces or through an uneven environment. Further, the construction of the vehicle restricts the legs to operating with only two degrees of freedom, which impairs the ability of the vehicle to traverse or cross over certain objects, particularly larger objects.
The principal considerations in designing a vehicle will depend to some extent on the environment in which it is to be used. For the particular example of a monitoring-type vehicle for use in the interior of a building, the vehicle must be narrow enough to fit through a standard doorway (approximately 30 inches). In addition, the overall system weight is important in that the weight must be maintained at a reasonable level such that power demands for the driving of the vehicle and joint actuation can be met with proven technology.
It is therefore an important object of the present invention to provide a hybrid robotic vehicle having enhanced ability to overcome or traverse articles or terrain, and operate in an obstacle-strewn environment.
It is another important object of the present invention to provide a hybrid robotic vehicle which has the ability to maintain a payload in a horizontal or other fixed attitude as the vehicle traverses uneven surfaces.
It is a further important object of the present invention to provide a robotic vehicle which is capable of operating in wheeled, tracked, or legged modes wherein a plurality of appendages having three degrees of freedom are attached to a main body containing or comprising the payload.